The In-cell touch screen is popular because the touch system can be integrated with the display screen so that the thickness of the whole liquid crystal display (LCD) can be reduced effectively and the manufacturing process can be simplified. LCD usually includes a color film substrate and an array substrate. In the In-cell touch screen, the touch system is usually disposed at the side of the color film substrate since the array substrate usually includes more circuit designs.
As shown in FIG. 1, a touch layer 100 is integrated at the side of the color film substrate in the In-cell touch screen. The touch layer 100 includes a plurality of drive lines 101 and sensing lines 102. The sensing lines 102 in each row are separated by the drive lines 101 and the separated sensing lines 102 in each row are connected by bridges 103 in the horizontal direction. Display function and touch function are integrated in the In-cell touch screen. Progressive scanning is performed on the drive lines of the touch layer to achieve the touch function, while progressive scanning is performed on gate lines on the array substrate to achieve the display function. The operating principle of touch detection is as follows: drive signals are applied to the drive lines, a signal change is detected on the sensing lines, X-directional coordinates are determined by the drive lines and Y-directional coordinates are determined by the sensing lines; during the detection, progressive scanning is performed on the X-directional drive lines, the signal on each sensing line is read when each of the driving lines is scanned, all the intersecting points of the rows and columns are gone through in a round of scanning, to determine the location of a touch action.
A time-sharing driving manner of display drive and touch drive is usually adopted for the In-cell touch screen. A scanning period T includes a display drive time duration T1 and a touch drive time duration T2, which means T=T1+T2. That is to say, in one scanning period T, the display drive scanning is completed in T1 and then the touch drive scanning is completed in T2. For the display drive, longer display drive time duration T1 means longer charging time of Thin Film Transistors (TFTs) on the array substrate and better display effect; for the touch drive, longer touch drive time duration T2 means better effect of touch detection. The display drive time duration T1 and the touch drive time duration T2 should both be extended in order to ensure both the display effect and the touch detection effect. Longer display drive time duration T1 and touch drive time duration T2 are needed especially for large-size and high-resolution touch display screens. Therefore, there may not be enough time to be allocated in one scanning period.
Accordingly, the drive method in which the display drive and the touch drive are driven simultaneously is also adopted in the industry. That is to say, the display drive scanning and the touch drive scanning are performed simultaneously in one scanning period, whereby the charging and discharging of the TFTs on the array substrate will be completed in the scanning period T. However, capacitive couplings may be generated from the charging and discharging of the TFTs and turn into noises that may affect the touch function and cause the problems of low signal noise ratio (SNR) for the touch control and even false touch.